Photographic emulsions



Dec. 5, 1961 J, w. GATES, JR., ETAL 3,011,890

PHOTOGRAPHIC EMULSIONS Filed. July 21, 1958 t' 40% replacement 3.

U U 3 w 60 3O |O%replucement 3 Q m i l 5 IO I5 Bromoocetic acid/[00goxidized soybean protein Fig. 2

4O %replocement x 20 U E U I 3 IO- 5 IO replacement g Y E U 0 i l 5 IOI5 20 Bromoocetic acid/g oxidized soybean protein JOH/V n. GATES JR PAULE. MILLER JAMES E. KOLLER INVENTORS United States Patent 3,011,890PHOTOGRAPHIC EMULSIONS John W. Gates, Jr., Paul E. Milier, and James E.Koller,

Rochester, N.Y., assignors to Eastman Kodak Company, Rochester, N.Y., acorporation of New Jersey Filed July 21, 1958, Ser. No. 749,635 5Claims. (Cl. 96-94) This invention relates to photographic emulsions inwhich certain protein derivatives are employed as a substantial portionof the carrier for the silver halide therein.

Ordinarily, photographic emulsions comprise a dispersion oflight-sensitive silver halide grains in a carrier for the silver halidewhich has usually been gelatin. Additives such as optical sensitizers,sensitizing dyes, hardeners, coating aids, and the like have also beenprovided to improve the properties of the emulsion in the mannerdesired.

The maximum optical density of the silver image of a photographic filmor paper after exposure, processing, and drying depends on the densitywhich results from the development process and the changes which occurduring the processing and drying procedure. The vehicle in which thesilver halide grains are suspended exerts an influence on the maximumdensity during both the processing and the drying of the emulsion layer.For instance, the maximum density of a film may be altered by varyingthe amount or type of hardening agent added to the photographic emulsionemployed.

One object of our invention is to provide photographic emulsions inwhich certain protein derivatives are employed therein. Another objectof our invention is to provide photographic emulsions having greatersilver covering power and less density loss upon drying thanphotographic emulsions in which these certain protein derivatives ortheir equivalent are absent. A further object of our invention is toincrease the speed and contrast of photographic emulsions. Other objectsof our invention will appear herein.

We have found that the partial replacement of the gelatin ingelatin-silver halide emulsions with certain modified proteins resultsin increased covering power, usually in both the wet and dry states, forthe silver which may be formed therein by exposure and development. Whento 50 percent of the carrier for the silver halide in such emulsions isa derivative of an oxidized protein as will be described herein, thecovering power of the developed silver in such emulsions while still ina wet condition after processing is usually greater than that of silverin emulsions containing the full amount of gelatin as a carrier.Furthermore, this difference is even greater after drying because lossof covering power on drying is smaller in emulsions containing theseprotein derivatives than in full gelatin emulsions. Such an increase ofcovering power results in increased contrast and maximum density andusually in increased effective speed where the latter is measured at adensity significantly above the fog level. In many cases in coarse-grainemulsions, speed gains in the toe regions of the sensi-tometric curvesresulted over and above those which could be attributed to increasedcovering power. The improvement is noted in use both in coarse-grainedand in fine-grained emulsions.

The protein derivatives which have been found to be useful in preparingemulsions in accordance with our invention are carboxymethy'latedproteins. It the protein is other than gelatin, the sulphur-containingcompounds inherent therein are desirably destroyed or removed byoxidation such as by treatment with hydrogen peroxide by the methoddescribed in U.S. Patent No. 2,691,582

ice

of Lowe and Gates. Any of the treated proteins described in that patentare useful as material to be carboxymethylated for obtaining proteinderivative useful as a supplement to the gelatin in photographicemulsions. The carboxymethyl protein is used in accordance with ourinvention in an amount 10-50% based on the total protein employed in theemulsion. V

The carboxymethylation of the protein is accomplished by reaction uponthe protein with an a halo fatty acid such as bromoacetic acid at a pHof 9-l2, such as is obtained by the presence of an alkaline buffermaterial in the reaction mass. The degree of carboxymethylation isusually in the range of 525% by weight. Some of the naturally occurring,amino'containing vegetable and animal proteins which may be oxidized andthen c-arboxymethylated and which will be useful in photographicemulsions in accordance with our invention are soybean protein, casein,edestin, glutin, blood albumin, egg albumin, castor bean protein andglobulin. Gelatin ordinarily does not need any comparable treatmentbefore forming a useful carboxyrnethylated product therefrom.

The following examples illustrate methods of preparing carboxymethylatedproteins useful in compositions in accordance with our invention.

Example 1 parts of casein was thoroughly mixed with 900 parts ofdistilled water at 45 C. The pH was adjusted to 11.0 by adding 20%sodium hydroxide, whereupon 5 parts of 30% hydrogen peroxide was addedand the solution was stirred for 15 minutes. An additional 5 parts of30% hydrogen peroxide was added and the solution was mixed for 1 hour.Coagulation was caused by adding sulfuric acid to a pH of 3.0. Thecasein coagulum resulting was separated from the liquid, washed withdistilled water, and was redispe'rsed in distilled water at 50 C. at apH of 9.0 to a volume of 1,000 mi. 10 parts of magnesium oxide and 10parts of bromoacetic acid were added and the solution was stirred for 3hours. The solution was then filtered. The casein derivative whichformed was obtained by coagulation with sulfuric acid at a pH of 3.0.The carboxymethy lated casein thus obtained was separated from theliquid, washed with distilled water, and was redispersed in distilledwater at 50 C. and at a pH of 5.5 to a volume of 1 liter.

Example 2 1,000 parts of casein was mixed with 9,000 parts of distilledwater at 50 C. 20% sodium hydroxide was added to adjust the pH to 11.0.50 parts of 30% hydrogen peroxide was added and the solution was stirredfor 15 minutes and then an additional 50 parts thereof was added and thesolution was stirred for 1 hour. Coagulation was caused by addingsulfuric acid to a pH of 3.0. The casein coagulum which formed wasseparated, washed with distilled water, and redispersed in water at 50C. to a volume of 8,500 ml. at a pH of 9. 98.5 parts of bromoacetic acid(dissolved in water) were added and the pH was maintained at 9 for 7hours with sodium hydroxide. The carboxymethylated casein thus obtainedwas coagulated'by adding sulfuric acid to a pH of 3.0. The coagulumwhich formed was separated by decanting the liquid, Washed withdistilled water, and was redispersed in 6,000 parts of 50 C. distilledWater to a pH of 5.6. The solution was mixed with parts of carbon for 30minutes and was then filtered. A clear solution of carboxymethyl caseinsuitable for use in preparing photographic emulsions was obtained.

Example 3 150 parts of soy protein was stirred into 1,350 parts ofdistilled water at 50 C. 20% sodium hydroxide was added to adjust the pHto 11.0. 7.5 parts of 30% hydrogen peroxide was added. The solution wasstirred for 15 minutes and then an additional 7.5 parts of 30% hydrgenperoxide was added and the solution was stirred for 1 hour. Half of thesolution was stirred for 6 hours with 15 parts of bromoacetic aciddissolved in 50 parts of distilled water, the pH being maintained at 9.5by the addition of 20% sodium hydroxide. Carboxymethylated protein wascoagulated by adding sulfuric acid to a pH of 3.0. The carboxymethylatedprotein thus obtained was collected, washed with distilled water, andredispersed in 500 parts of 50 C. distilled water at a pH of 6.0. Thedispersion was treated with 15 parts of purifying carbon for 30 minutesand was then filtered.

Example 4 300 parts of soy protein was stirred into 2,700 parts ofdistilled water at 50 C. 20% sodium hydroxide was added to convert thepH to 11.0. There was then added 15 parts of 30% hydrogen peroxide, thesolution was stirred for 15 minutes and an additional 15 parts of 30%hydrogen peroxide was added with stirring for 1 hour. 30 parts ofbromoacetic acid dissolved in 100 parts of distilled water was added to/2 of the solution, the mass was stirred for 6 hours and the pH was heldat 9.5 with sodium hydroxide. Sulfuric acid was then added to impart apH of 2.5 whereupon the carboxymethylated protein formed coagulated. Thecoagulum was collected, washed with distilled water, and redispersed in1,000 parts of 50 C. distilled water at a pH of 6.0. The dispersion wastreated with carbon for 30 minutes and was then filtered.

. Example 450 parts of soy bean protein was stirred into 4050 parts ofdistilled water at 50 C. 20% sodium hydroxide was added to adjust the pHto 11.0. 22.5 parts of 30% hydrogen peroxide was added, the solution wasstirred for 15 minutes, an additional 22.5 parts was added and thesolution was stirred for 1 hour. It was then divided into 3 equal parts.One part was stirred for 4 hours with 7.5 parts of bromoacetic aciddissolved in 25 parts of distilled water, the pH being maintained at 9.5with sodium hydroxide. The carboxymethylated protein thus obtained wascoagulated at a pH of 2.5 obtained by adding sulfuric acid. The coagulumwas collected, washed with distilled water, redispersed in distilledwater which dispersion was mixed with carbon for 20 minutes and was thenfiltered.

Example 6 ,There was added to a second part of the soy bean proteinsolution of the preceding example 15 parts of bromoacetic acid dissolvedin water, the procedure otherwise being the same as in Example 5.

Example 7 Example 9 150 parts of soy protein was mixed with 1350 partsof distilled water at C. 20% sodium hydroxide was added to raise the pHto 11. 7.5 parts of 30% hydrogen peroxide was added, the solution wasstirred for 15 minute's, an additional 7.5 parts of hydrogen peroxidewas added, and the solution was stirred for 1 hour. The pH wasmaintained at 9.5 for 3 hours after the addition to the'solution of 15parts of bromoacetic acid dissolved in 50 parts of distilled water. Theresulting solution was treated with 15 parts of carbon for 20 minutesand was filtered. The protein derivative formed was coagulated by addingsulfuric acid to impart a pH of 2.5. The coagulum was washed andredispersed in distilled water, held at a pH of 5.6 by the occasionaladdition of sodium hydroxide.

Example 10 100 parts of bone gelatin were plumped and dissolved in 1900parts of distilled water and the pH of the solution was brought to 9.0by adding 25 parts of magnesium oxide.

There was then added 20 parts of bromoacetic acid and an additional 25parts of magnesium oxide was added to keep the pH above 9.0. The massstood for 18 hours at room temperature, then was warmed to 35 C. and wasstirred for 8 hours. The gelatin stood for an additional 18 hourswhereupon the temperature was raised to 45 C. The solution was filtered,chilled, sliced, washed and dried in the normal manner to obtaincarboxymethylated gelatin, adapted to use in preparing photographicemulsions.

Example 13 400 parts of bone gelatin were plumped in 3600 parts ofwater. The temperature was raised to 35 C. to melt the gelatin. 50 partsof magnesium oxide and parts of bromoacetic acid were added and the masswas held at 35 C. for 8 hours. An additional 50 parts of magnesium oxidehad been added to keep the pH above 9.0. Upon completion of thereaction, the pH was adjusted to 6.0 with sulfuric acid and the productobtained was filtered, chilled, washed and dried in a normal manner.

Example 12 400 parts of bone gelatin ware plumped in 3600 parts ofwater. The temperature was raised to 35 C., melting the gelatin. 50parts of magnesium oxide and 40 parts of bromoacetic acid were added andthe solution was held at 35 C. for 8 hours. Sulfuric acid was then addedto drop the pH to 6.0. The material was removed by filtering and waschilled, washed and dried in the usual manner.

Example 13 200 parts of bone gelatin were plumped in 1800 parts ofwater. The gelatin was melted at 50 C. and 25 parts of magnesium oxidewere added thereto. 10' parts of bromoacetic acid (dissolved in water)was then added and the solution was stirred at 50 C. for 3 hours. Thesolution was then filtered and sulfuric acid was added to adjust the pHto 6.0. The carboxymethyl gelatin thus obtained was chilled, sliced,washed and dried in the usual manner.

The following examples illustrate the use of cat-boxymethyl proteins inconjunction with gelatin as a carrier for silver halides in photographicemulsions. Our invention comprises the utilization of oarboxymethylatedproteins having no photographically active impurities therein orproteins which may be purified by known methods such as oxidation toremove photographically active materials.

Example 14 A coarse-grained gelatin-silver bromoiodide emulsion of atype employed for making a screen X-ray film and containing 36 grams ofgelatin per mole of silver halide was prepared for coating by adding asolution of a coating aid and a suitable antifoggant. The emulsion wasdivided into 2 parts as follows:

(a) 1440 cos. of a 10% solution of gelatin were added per mole of silverhalide.

(b) 720 cos. of a 10% solution of gelatin and 950 cos. of 7.6% solutionof carboxymethyl casein, as prepared in Example 1, were added per moleof silver halide.

Suitable hardener was then added to each of these emulsions and theywere coated onto a cellulose acetate film support at a coverage of 200square feet per mole of silver halide. 1 strip of each coating wasexposed in an Eastman 1B sensitometer through a continuous step wedge,developed 3 minutes in a rapid X-ray developer, fixed and washed.Densities of the steps on each strip were thendetermined before andafter drying. The results obtained were tabulated as follows:

Part D-inax. D-max. Percent Relative 7 wet dry D. Loss Speed Example Anemulsion similar to that used in Example 14 except that it contained 107grams of gelatin per mole of silver halide was prepared for coating asin Example 14.- The emulsion was divided into 4 parts as follows:

After addition of hardeners each of these emulsions were coated out ontocellulose acetate film supports and strips thereof were tested asdescribed in Example 14. In addition, unprocessed strips of each coatingwere analyzed for silver coverage. The results obtained were tabulatedAn emulsion similar to that of Examples 14 and 15 and containing 107grams of gelatin per mole of silver halide was prepared for coating asin Example 14. The material was divided into 6 parts as follows:

(a) 720 cos. of a 10% solution of gelatin per mole of silver halide wasadded.

(b) 600 ccsof a 12% solution of car-boxymethylated oxidized soybeanprotein prepared in accordance with Example 9 was added per mole ofsilver halide. The protein used was known as Drackett 112A.

(0) 600 ccs. of a 12% solution of carboxymethyl-ated oxidized soybeanprotein similar to that prepared in accordance with Example 9 was addedper mole of silver halide. The protein used was known as Drackett 112B.

((2!) 555 cos. of a 13% solution of carboxymethylated oxidized soybeanprotein similar to that prepared in accordance with Example 9 was addedper mole of silver halide. The protein used was known as Drackett 112C.

(e) 570 ccs. of a 12.6% solution of carboxymethylated oxidized soybeanprotein similar to that prepared in Example 9 was added per mole ofsilver halide. The protein was known as Drackett 220.

U (f) 545 ccs. of a 13.2% solution of carboxymethylated oxidized soybeanprotein similar to that prepared in Example 9 was added per mole ofsilver halide. The protein used was known as Drackett 410.

These separate emulsions were coated onto cellulose acetate filmsupports and strips thereof were tested in the manner described inExample 14. The results obtained were tabulated as follows:

Part D-max D-max. Percent Relative 7 wet dry Loss of D Speed Example 17An emulsion similar to that used in Example 15 was prepared for coatingas described in Example 14. The material was divided into 9 parts, to 1of which was added 720 ccs. of 10% gelatin solution per mole of silverhalide (part a). T o the other parts were added individually:

(b) Carboxymeth-yl oxidized soybean protein prepared with 20 grams ofbromoacetic acid per 100 gnams of protein in accordance with Example 4.

(c) Carboxymethyl oxidized soybean protein prepared with 15 grams ofbromoacetie acid per 100 grams of protein in accordance with Example 7.

(d) Carboxymethyl oxidized soybean protein prepared with 10 grams ofbromoaeetie acid per 100 grams of protein in accordance with Example 6.

(e) Carboxymethyl oxidized soybean protein prepared with 5 grams ofbromoacetic acid per 100 grams of protein as described in Example 5.

in quantities equal in dry weight to that of the gelatin added to part aand to the second set of parts (7, g, h and i) at this level but withadditional gelatin to keep the total weight of protein in all samplesconstant. These parts were coated out onto cellulose acetate filmsupports and strips taken from each were tested as described in Example14.

The results obtained were plotted on graphs illustrated by FIGS. 1 and 2of the drawing. In the accompanying drawing FIG. 1 is a graphicalrepresentation based on relative speeds and FIG. 2 is a graphicalrepresentation based on maximum densities to indicate the improvementupon greater replacement of the gelatin of the photographic emulsion bycarboxymethylated soybean protein.

Example 18 A coarse-grained gelatin-silver bromoiodide emulsion suitablefor use in the preparaiton of high speed blackand-white negative filmwas prepared for coating by 7 adding thereto solutions of coating aidand antifoggant.

The emulsion was divided into five parts as follows:

These separate parts were each coated onto cellulose acetate filmsupport and were tested in the manner described in Example 14 exceptthat several strips were exposed and then developed in variousdevelopers for varying periods of time. The results obtained aretabulated below:

Relative Speed -y 4 Kodak 5 Kodak 12 12' Part D-19 DK-50 Kodak 4 D-19 5Kodak De- De- Rapid De- DK-5O Rapid veloper veloper X-ray veloper De-X-ray Developer Developer veloper Example 19 A fine-grain gelatin-silverchlorob-romide emulsion containing 119 grams of gelatin per mole ofsilver halide was prepared for coating by adding coating aid thereto.The material was divided into 3 parts as follows:

(a) No further additions.

(b) 900 cos. of a 10% solution of gelatin per mole of silver halide wasadded.

(c) 920 cos. of a 9.8% solution of carboxymethyl casein per mole ofsilver halide was added.

Suitable hardener was added to each and these parts were coated ontocellulose acetate supports at a coverage of 300 square feet per mole ofsilver halide. The coatings were tested in the manner described inExample 14 with development in Kodak DK-50 developer for 5 minutes. Theresults obtained are as follows:

Part D-max. 'y

(a) 1. s9 2. 26 (b) 2. 03 2. 40 (c) 2. 51 2. so

Example 20 An emulsion similar to that used in Example 14 was preparedfor coating and divided into 3 parts as follows:

These parts were coated onto cellulose acetate film support and testedin the manner described in Examples 14 and 15. The results obtained wereas follows:

g. Ag per D'max. D Dry, Relative 1 Part sq. ft. Dry g. Ag it. SpeedExample 21 'An emulsion similar to that used in Example 14 was preparedfor coating and divided into 5 parts as follows:

(a) 1440 cos. of a solution of gelatin per mole of silver halide wereadded.

(b) 360 cos. of a 10% solution of gelatin and 1080 cos. of carboxymethylgelatin as described in Example 10 were added per mole of silver halide.

(0) Like b only the carboxymethyl gelatin added was that as prepared bythe procedure of Example 11.

8 (d) Like b only the carboxymethyl gelatin added was that as preparedin Example 12. (e) Like b only the carboxymethyl gelatin added was thatas prepared in Example 13.

These parts were coated and strips thereof were tested as the mannerdescribed in Example 14. The results obtained were as follows:

Part Relative 'y Fog D-rnax.

Speed Dry (a) 100 1. 00 .06 1. 72 (b) 132 2.08 06 1. 75 (c) 123 1. 9406 1. 75 (d) 121 2.10 06 1. 78 (e) 121 1. 80 06 1. 65

The emulsions in accordance with our invention may, if desired, bechemically sensitized by any of the accepted procedures. For instance,these emulsions can be digested with naturally active gelatin, orsensitized sulphur compounds can be added such as those described inSheppard U.S. Patent Nos. 1,574,944 and 1,623,499, and in Sheppard andBrigham 2,410,489.

The emulsions can also be treated with salts of the noble metals such asruthenium, rhodium, palladium, iridium and platinum, all of which belongto group VIII of the periodic table of elements and have an atomicweight greater than 100. Representative compounds are ammoniumchloropalladate, potassium chloroplatinate and sodium chloropalladite,which are used for sensitizing in amounts below that which produces anysubstantial fog inhibition, as described in Smith and Trivelli U.S.Patent 2,448,060, and as antifoggants in higher amounts, as described inTrivelli and Smith U.S. Patents 2,566,245 and 2,566,263.

The emulsions can also be chemically sensitized with gold salts asdescribed in Waller and Dodd U.S. Patent 2,399,083 or stabilized withgold salts as described in Damschroder U.S. Patent 2,597,856 and Yutzyand Leermakers U.S. Patent 2,597,915. Suitable compounds are potassiumchloroaurite, potassium aurithiocyanate, potassium chloroaurate, aurictrichloride and 2-aurosulfobenzothiazole methochloride.

The emulsions can also be chemically sensitized with reducing agentssuch as stannous salts (Carroll U.S. Patent 2,487,850), polyamines suchas diethylene triamine (Lowe and Jones U.S. Patent 2,518,698),polyamines, such as spermine (Lowe and Allen U.S. Patent 2,521,925 orbis-(,B-aminoethyl) sulfide and its water-soluble salts (Lowe and JonesU.S. Patent 2,521,926).

The emulsions can also be stabilized with the mercury compounds ofAllen, Byers and Murray U.S. Patent 2,728,663, Carroll and Murray U.S.Patent 2,728,664, and Leubner and Murray U.S. Patent 2,728,665, thetetrazaindenes of Carroll U.S. Patent 2,716,062, and the quaternarybenzothiazolium compounds of Brooker and Stand U.S. Patent 2,131,038.

The emulsions may also contain speed-increasing compounds of thequaternary ammonium type of Carroll U.S. Patent 2,271,623, Carroll andAllen U.S. Patent 2,288,226, and Carroll and Spence U.S. Patent2,334,864, and the polyethylene glycol type of Carroll and Beach U.S.Patent 2,708,162.

We claim:

1. A photosensitive silver halide emulsion comprising silver halidecarried by a protective colloid essentially consisting of proteinmaterial, 10-50% of which is photographically inert carboxymethylatedprotein substantially the remainder of the protein material beinggelatin.

2. A photosensitive silver halide emulsion comprising silver halidecarried by a protective colloid essentially consisting of a mixture ofgelatin and photographically inert carboxymethylated gelatin, the latterbeing 10-50% of the mixture.

3. A photosensitive silver halide emulsion comprising silver halidecarried by a mixture essentially consisting of gelatin andphotographically inert carboxymethylated oxidized casein, the latterbeing 1050% of the mixture.

4. A photosensitive silver halide emulsion comprising silver halidecarried by a protective colloid essentially consisting of a mixture ofgelatin and photographically inert carboxymethylated soy protein, thelatter being 105 0% of the mixture.

5. A photosensitive silver halide emulsion comprising silver halidecarried by a mixture of gelatin and photographically inertcarboxymethylated blood albumin, the latter being l0-50% of the mixture.

References Cited in the file of this patent UNITED STATES PATENTS

1. A PHOTOSENSITIVE SILVER HALIDE EMULSION COMPRISING SILVER HALIDECARRIED BY A PROTECTIVE COLLOID ESSENTIALLY CONSISTING OF PROTEINMATERIAL. 10-50% OF WHICH IS PHOTOGRAPHICALLY INERT CARBOXYMETHYLATEDPROTEIN SUBSTANTIALLY THE REMAINDER OF THE PROTEIN MATERIAL BEINGGELATIN.